CN107401462B

CN107401462B - Method and system for operating an engine

Info

Publication number: CN107401462B
Application number: CN201710320110.XA
Authority: CN
Inventors: J·狄克逊; I·哈莱罗恩; A·爱莱瓦洛
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2016-05-18
Filing date: 2017-05-09
Publication date: 2021-10-26
Anticipated expiration: 2037-05-09
Also published as: EP3246549A1; CN107401462A; EP3246549B1; RU2017112942A; MX2017006053A; RU2017112942A3; US20200232402A1; RU2730216C2; US10677179B2; US20170335780A1; US11053872B2

Abstract

The invention relates to a method and a system for operating an engine. Methods and systems are provided for coordinating operation of a high pressure EGR control loop with a boost pressure control loop. In one example, after the accelerator pedal is stepped on, the turbine vane position may be adjusted according to the maximum allowable exhaust pressure upstream of the turbocharger turbine. The maximum allowable exhaust pressure is determined based on the HP EGR valve position at tip-in.

Description

Method and system for operating an engine

Cross Reference to Related Applications

This application claims priority to uk patent application No.1608717.3 filed on day 5, month 18 of 2016 and to indian patent application No.201641017210 filed on day 5, month 18 of 2016. The entire contents of the above-referenced application are hereby incorporated by reference in their entirety for various purposes.

Technical Field

The present description relates generally to methods and systems for controlling a vehicle engine to improve responsiveness of engine components to control inputs.

Background

Engines for vehicles (e.g., motor vehicles) typically include a turbocharger that includes a compressor configured to increase the pressure of inlet air entering the engine and, thus, increase the amount of fuel that may be combusted within the engine to provide torque to drive the vehicle. The compressor is driven by an exhaust turbine. The turbocharger responds to a request from the vehicle operator for increased torque supplied by the engine. A boost (boost) control loop controls the turbocharger to provide the desired boost pressure in the intake manifold, thereby controlling the mass of gases entering the engine. In this way, the boost circuit improves engine performance and the driver's driving experience.

Engines are also commonly provided with Exhaust Gas Recirculation (EGR) systems configured to recirculate a portion of the combusted exhaust gas to an inlet of the engine. Replacing a portion of the oxygen-enriched inlet air with combusted exhaust gas reduces the proportion of the contents available for combustion per cylinder. This results in lower heat release and lower peak cylinder temperatures and thus reduced NOx formation, thereby improving vehicle emissions performance. An EGR control loop of the engine controls the flow of exhaust gas from the exhaust manifold to the intake manifold. In a boost engine, the EGR system may include a high pressure EGR line for recirculating exhaust gas from upstream of the turbine to downstream of the compressor, and a low pressure EGR line for recirculating exhaust gas from downstream of the turbine to upstream of the compressor.

EGR is related to the operation of the turbocharger system, and therefore both systems need to be carefully controlled to provide the driver with a good response to a request for increased torque from the engine, while maintaining good emissions performance. In the event of excessive exhaust gas recirculation, the torque response of the engine may be poor, which may affect the driving experience. On the other hand, if an insufficient amount of exhaust gas is recirculated, NOx emissions increase. In addition, with stricter emission control regulations, EGR is greatly relied upon to control emissions, while customer demand for fast response engines is increasing. Such competing and conflicting requirements often result in damage to one of the two gas control circuits (i.e., the boost circuit and the EGR circuit).

As one example, when the driver requests increased torque to be supplied from the engine, the operation of the turbocharger is controlled to increase the boost pressure as quickly as possible, for example, by depressing an accelerator pedal (also referred to as a tip-in pedal) of the vehicle. For example, the blades of the turbine may be moved to a more closed position in order to increase the inlet pressure of the engine. However, rapid closing of the vanes causes an increase in exhaust manifold pressure, which in turn results in an increase in the pressure drop across the EGR line. Additionally, if the position of the EGR valve of the EGR line remains unchanged, the increase in pressure drop causes an increase in EGR flow. Thus, the amount of fresh charge in the intake manifold may be reduced. The engine may thus provide an inappropriate response to a request for increased torque. Thus, torque production may be reduced, rather than having increased torque production, which may adversely affect the boost circuit, and thus adversely affect the driving experience.

One example method for controlling boost pressure in an internal combustion engine is described in european patent application 1178192 (' 192 application). Wherein vanes of a turbine of the engine are adjusted to control boost pressure in the intake passage. Specifically, the vanes are adjusted based on engine operating conditions such as engine speed, fuel and oil consumption, water temperature, boost pressure, barometric temperature, and position of the EGR valve.

However, the inventors herein have recognized potential issues with such systems. As one example, the' 192 application describes vane adjustment for controlling pressure downstream of a turbine based on a plurality of parameters. As such, the method of the 192 application may not be able to control the pressure upstream of the turbine. As another example, the' 192 application provides a static mechanism for controlling vane position that may not properly optimize the EGR circuit and the boost circuit if a quick response may be required.

Disclosure of Invention

In one example, the above-described problem may be solved by a method for a turbocharged engine, the method comprising: estimating a maximum allowable rate of increase of Exhaust Manifold (EM) pressure based on a position of an Exhaust Gas Recirculation (EGR) valve; estimating a maximum allowable EM pressure based on a maximum allowable rate of increase of EM pressure; and adjusting a blade position of the exhaust turbine based on the maximum allowable EM pressure. In this way, EGR and boost pressure control may be better coordinated for fast torque response. Specifically, the method enables maintenance of Exhaust Manifold (EM) pressure of an engine.

As one example embodiment, a turbocharged engine may be operated with high pressure EGR and boost enabled. At each time step of boost engine operation, or in response to an operator torque request, the engine controller may determine an Exhaust Manifold (EM) pressure, i.e., exhaust pressure upstream of a turbine of a turbocharger. The exhaust pressure upstream of the turbine may be determined by reference to a data model or a look-up table.

The controller may additionally determine a maximum permitted rate of increase of the EM pressure based on a position of an Exhaust Gas Recirculation (EGR) valve. The maximum permitted rate of increase may correspond to a maximum permitted rate for a given position of the EGR valve. Additionally, at each time step, the maximum allowable EM pressure may be determined based on the rate of increase of the EM pressure. The maximum allowable pressure indicates the EM pressure to maintain the mass flow of recirculated exhaust gas within permissible limits. In one example, the maximum allowable pressure value may be determined by: multiplying the maximum permitted rate of increase in pressure by a particular time period (e.g., the length of a time step in which the method is performed) to calculate a maximum permitted increase in pressure; and then adding the maximum permitted increase to the determined exhaust pressure upstream of the turbine.

Thus, based on the maximum allowable EM pressure, at each time step, operation of the turbocharger may be controlled based at least in part on the exhaust pressure upstream of the turbine such that the rate of increase of the exhaust pressure is maintained at or below the maximum permitted rate. In one example, the turbocharger may include a Variable Geometry Turbine (VGT), wherein operation of the turbocharger assembly may be controlled by varying the geometry of the VGT. For example, the position of the blades of the turbine of the internal combustion engine may be controlled such that the EM pressure is maintained at or below a maximum allowable EM pressure and/or a maximum permitted rate of increase in EM pressure. Additionally or alternatively, the turbocharger may include a turbocharger assembly bypass conduit configured to permit exhaust gas to bypass the turbocharger assembly. For example, the bypass conduit may allow exhaust gas to bypass a turbine of the turbocharger assembly. Wherein operation of the turbocharger assembly may be controlled by varying exhaust gas flow through the bypass conduit by varying a position of the bypass valve in the bypass conduit. Herein, the maximum allowable EM pressure and/or the maximum allowable rate of increase in EM pressure may be determined based at least in part on a position of the EGR valve. The controller may additionally determine a mass flow rate of exhaust gas through the turbine. Operation of the turbocharger may be controlled based at least in part on the mass flow rate of exhaust gas through the turbine.

As another example, the controller may control the degree and/or speed of closure of the blades of the turbine based on the maximum allowable EM pressure to optimize the EGR loop and boost loop of the internal combustion engine. For example, the speed at which the turbine blades are closed may be controlled by controlling the blade position.

In one example, to control turbine blade position, the position of the blades may be determined based on a reverse turbine model. The inverse turbine model may set the vane position based on the maximum allowable EM pressure, the exhaust pressure downstream of the turbine, and the mass flow rate of the exhaust gas in the turbine. Additionally, the determined blade position may be compared to a default value for blade position. The default value refers to a value of the vane position that is determined independently of the maximum allowable pressure. Based on the comparison, the minimum of the two values may be determined and used as the final value for the blade position.

As one example, the method may be performed iteratively over a plurality of time steps. Each step of the method may be performed during each time step. Alternatively, one or more of the steps may be omitted when performed within an iterative process. Iterations of the steps of the method may continue until a predetermined period of time has elapsed. In another example, the controller may detect a request for an increased amount of torque supplied by the engine, for example, a request from a driver or a controller of the vehicle. The method may be iteratively performed over a plurality of time steps in response to detecting a request for increased torque.

The controller may additionally vary the position of the EGR valve such that the flow rate of exhaust gas within the EGR conduit remains substantially constant. Operation of the turbocharger may be controlled such that the position of the EGR valve may be changed to maintain the flow rate of exhaust gas within the EGR conduit at a substantially constant value.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

Drawings

FIG. 1 is a schematic illustration of an engine assembly according to an arrangement of the present disclosure;

FIG. 2 illustrates an example method of operating an engine assembly according to this disclosure;

FIG. 3 illustrates an example relationship between HP-EGR valve position and a maximum allowable rate of increase of EM pressure; and

FIG. 4 illustrates a contemplated example engine operation for coordinating an EGR control loop and a boost control loop.

Detailed Description

Engines equipped with Exhaust Gas Recirculation (EGR) generally have two gas control circuits, namely a boost circuit and an EGR circuit. These two circuits have significant interactions, wherein increasing the performance of one circuit may adversely affect the other circuit. For example, in the event of a sudden increase in torque demand, the mass flow of EGR may exceed a desired level if the EGR circuit does not respond quickly enough to an increase in exhaust manifold pressure. Additionally, if the change in exhaust manifold pressure is abrupt, the EGR circuit may not be able to adequately attenuate the effect, causing excessive burned gas in the intake system, resulting in a loss of torque. An example engine system having EGR capability is described with reference to FIG. 1. The engine controller may be configured to execute a control routine, such as the example routine of FIG. 2, to coordinate the engine EGR control loop and the boost control loop. Where the VGT geometry may be adjusted based on the position of the high pressure EGR valve, such as based on the relationship shown in fig. 3, to limit the maximum exhaust manifold pressure upstream of the exhaust turbine. Example engine operation is illustrated with reference to FIG. 4.

Referring to FIG. 1, an engine assembly 100 is shown according to an embodiment of the present subject matter. The engine assembly 100 may be coupled in a vehicle (e.g., an automotive vehicle), which may be a hybrid vehicle. The engine assembly 100 includes an engine 4, an intake system 6, and an exhaust system 8. The engine 4 is communicatively coupled to a control unit 110, which control unit 110 may be configured as an engine control unit. The intake air is mixed with fuel in cylinders 5 of the engine 4 and the fuel is combusted to provide power to drive the engine 4.

The engine intake system includes an intake manifold 115 to receive air for combustion via an intake passage 6 a. Fresh air may be provided to the engine through air filter 125 via intake passage 6 a. The air cleaner 125 prevents abrasive substances and contaminants, such as pollutants, pollen, dust, and bacteria, from entering the engine cylinder 5. In the vicinity of the air filter 125, a mass flow sensor 135 may be provided to determine the mass flow rate of air entering the engine 4. The mass flow sensor 135 may be coupled to the control unit 110 to provide the determined mass flow rate to the control unit 110 for controlling engine operation. Intake of air into the intake manifold 115 may be regulated using an intake throttle 145. The throttle 145 may be opened or closed to manage air flow. The pressure of the intake air, including fresh air and exhaust gas, entering the intake manifold 115 may be measured using a manifold charge pressure sensor 136, which pressure sensor 136 is also coupled to the control unit 110.

In the depicted example, the engine is a boosted engine system having a turbocharger assembly 14. Turbocharger assembly 14 includes an intake air compressor 130 driven by an exhaust turbine 150 via a shaft 152. The intake air may be compressed using the compressor 130 to increase the pressure and density of the air for better engine efficiency. The temperature of the intake air may increase due to compression. Thus, the compressed air may be cooled after passing through the charge air cooler 140 to reduce the temperature of the air prior to delivery to the engine to improve combustion.

The air induction system 6 includes a Low Pressure (LP) intake conduit (inlet product) 6a disposed upstream of the compressor 130 of the turbocharger assembly 14. The compressor 130 is configured to increase the pressure of the inlet air reaching the compressor 130 from the low pressure intake conduit 6a to a boosted pressure level. The inlet air that has been compressed by the compressor 130 enters the high pressure inlet duct 6 b. The inlet air flows within the HP inlet conduit 6b to the inlet manifold 115 of the engine and may be drawn into the cylinders 5 of the engine 4.

The exhaust system 8 also includes an exhaust manifold 120 to discharge exhaust gas after combustion in the engine. Exhaust system 8 may also include one or more exhaust aftertreatment devices 18 disposed downstream of turbine 150. For example, exhaust system 8 may include a lean NOx trap 18a, a particulate filter 18b, and/or a selective catalytic reduction device 18 c. The exhaust aftertreatment device may be configured to reduce a concentration of a pollutant present within the exhaust gas.

One or more of the

exhaust aftertreatment devices

18a, 18b, 18c may be controllable to adjust an efficiency of the exhaust aftertreatment devices in removing pollutants from the exhaust. Controlling the operation of the exhaust aftertreatment device may affect the mass flow rate of exhaust gas through the exhaust system 8 and, thus, through the turbine 150.

Additionally or alternatively, performance of the exhaust aftertreatment device 18 may be reduced after a period of operation of the device 18. For example, particulate filter 18b and/or lean NOx trap 18a may become full, thereby reducing the rate at which the particulate filter and/or lean NOx trap can remove pollutants from the exhaust. When the performance of the exhaust aftertreatment device decreases, the mass flow rate of the exhaust gas through the exhaust aftertreatment device and/or the pressure differential across the exhaust aftertreatment device may change.

The engine system 100 also includes a High Pressure (HP) Exhaust Gas Recirculation (EGR) assembly 160 for recirculating exhaust gas from upstream of the turbine to downstream of the compressor. The engine system also includes a Low Pressure (LP) Exhaust Gas Recirculation (EGR) assembly 170 for recirculating exhaust gas from downstream of the turbine to upstream of the compressor.

Exhaust gas may flow to the turbine 150 of the turbocharger assembly through the HP exhaust conduit 9 b. The exhaust gas may be expanded through the turbine 150 to reach the low pressure exhaust conduit 9 a. Power may be generated by the turbine 150 by expanding the exhaust gas through the turbine 150 to power the compressor 130.

In the depicted example, the turbine 150 is a Variable Geometry Turbine (VGT) that includes variable inlet vanes (not shown) that are arranged at an angle relative to a rotor (not shown) of the turbine. By varying the angle of the inlet vanes relative to the rotor, the power generated by the turbine 150, and thus the power provided to the compressor 130, can be controlled. The level of boost provided by the turbocharger assembly 14 may thus be controlled by varying the angle of the variable inlet vanes. In some arrangements, the geometry of the turbine 150 may be fixed.

The level of boost provided by the turbocharger assembly 14 may additionally or alternatively be controlled by controlling the flow of exhaust gas through the turbocharger assembly bypass conduit 154. The bypass conduit 154 is configured to allow a portion of the exhaust gas to flow from the HP exhaust conduit 9b to the LP exhaust conduit 9a without passing through the turbine 150. The flow of exhaust gas through the turbine bypass conduit 154 may be controlled by a bypass valve, also referred to as a wastegate valve 156. By allowing a portion of the exhaust gas to bypass the turbine 150, the power generated by the turbine, and thus the power available to drive the compressor 130, may be reduced. The level of boost provided by the turbocharger assembly 14 may thus be reduced.

In arrangements where the exhaust system 8 includes a VGT turbine and also includes a turbocharger bypass conduit 154 and a bypass valve 156, the power generated by the turbine 150 may be controlled by changing the geometry of the turbine 150 and/or by changing the position of the bypass valve 156.

As mentioned above, increasing the pressure of the inlet air into the engine 4, such as increasing the boost level or boost pressure, allows a greater amount of air to be drawn into the cylinders of the engine, which in turn allows more fuel to be mixed with the air and combusted. Combusting more fuel in the engine 4 allows the engine to produce more power and torque to propel the vehicle. When the driver of the vehicle requests more power to be supplied by the engine 4, for example by depressing an accelerator pedal (not shown) of the vehicle, the turbocharger assembly 14 may be controlled to increase the level of boost provided by the turbocharger assembly, and thus the power and torque generated by the engine.

HP EGR assembly 160 includes HP EGR conduit 12 configured to recirculate a portion of the exhaust gas exiting engine 4 back to intake system 6. The recirculated exhaust gas mixes with inlet air within intake system 6 and may be drawn back into engine 4 after passing through HP EGR cooler 164. The first end 12a of the HP EGR conduit may be coupled to the HP exhaust conduit 9b and in fluid communication with the HP exhaust conduit 9b, e.g., at a location on the exhaust system 8 upstream of the turbine 150. For example, first end 12a of HP EGR conduit 12 may be coupled to exhaust manifold 120. Second end 12b of HP EGR conduit 12 may be coupled to HP intake conduit 6b and in fluid communication with HP intake conduit 6b, e.g., at a location on intake system 6 downstream of compressor 130.

Exhaust flow within HP EGR conduit 12 may be controlled via HP EGR valve 162. The flow rate of exhaust gas may depend on the position of HP EGR valve 162 and the pressure differential between first end 12a and second end 12b of HP EGR conduit 12. For example, as the pressure of the exhaust gas within HP exhaust conduit 9b increases relative to the inlet gas pressure within HP inlet conduit 6b, the flow rate of the exhaust gas within HP EGR conduit 12 may increase for a given position of HP EGR valve 162.

LP EGR assembly 170 includes LP EGR conduit 17 configured to recirculate a portion of the exhaust gas exiting engine 4 back to intake system 6. The recirculated exhaust gas mixes with inlet air within the intake system 6 and may be drawn back into the engine 4 after passing through the LP EGR cooler 174. Exhaust flow within the LP EGR conduit 17 may be controlled by the LP EGR valve 172. The flow rate of the exhaust gas may depend on the position of the LP EGR valve 172 and the pressure differential between the ends of the LP EGR conduit 17.

Increasing the flow rate of the EGR gas due to a change in the position of the HP EGR valve or a change in the pressure differential across HP EGR conduit 12 may cause a decrease in the amount of inlet air present in the intake air drawn into the cylinders of engine 4, thereby decreasing the amount of fuel that may be combusted within the engine. The power generated by the engine 4 can thus be reduced. Controlling the power generated by the engine in this manner may be beneficial because controlling in this manner may result in a reduction in the production of pollutants such as nitrogen oxides as compared to controlling the engine 4 in other ways (e.g., by using an inlet throttle).

As described above, when the driver of the vehicle requests increased power or torque, the operation of the turbocharger assembly 14 may be controlled to increase the level of boost provided. In one example, controlling the turbocharger assembly to increase the boost level may be accomplished by adjusting the angle of the variable vanes of the turbine 150. Angling the vanes may reduce the area through which exhaust gas passing through the turbine 150 may flow. Thus, after controlling the turbine in this manner, the exhaust pressure upstream of the turbine (e.g., within exhaust manifold 120) may increase.

As another example, controlling the turbocharger assembly to increase boost level may be accomplished by closing the wastegate valve 156. Closing the wastegate valve may reduce the flow area available for exhaust gas to bypass the turbine 150, which may cause an increase in exhaust pressure within the HP exhaust conduit 9b and/or the exhaust manifold 120.

The increase in exhaust pressure upstream of the turbine 150 due to the change in flow area past and/or around the turbine may occur at a higher rate than the increase in inlet gas pressure within the HP intake conduit 6b due to increased power being supplied to the compressor 130 (e.g., through the turbine 150). This may cause a change in the pressure differential between first end 12a and second end 12b of HP EGR conduit 12, which may affect (e.g., increase) the flow rate of EGR gas within the HP EGR conduit.

Thus, when the driver requests an increase in the power supplied by the engine, the interaction between the turbocharger assembly 14 and the operation of the HP EGR system 160 may cause an undesirable decrease in the power provided by the engine 4.

The position of HP EGR valve 162 may be controlled based at least in part on the pressure differential across HP EGR conduit 12, and thus HP EGR valve 162 may be controlled to compensate for this effect. However, if the driver requests a rapid increase in power supplied by the engine, HP EGR valve 162 may not be controlled quickly enough to adequately compensate for changes in the pressure differential across HP EGR conduit 12.

The control unit 110 receives signals from the various sensors of FIG. 1 and employs the various actuators of FIG. 1 to adjust engine operation based on the received signals and instructions stored on the controller's memory. In one example, a controller optimizes a boost circuit and an EGR circuit of an engine to control and coordinate emissions and enhance engine performance. To optimize both circuits, the control unit 110 provides for limiting the rate of change of the Exhaust Manifold (EM) pressure (P3) to a level that can be responded to correctly, thereby reducing interference with the boost circuit. The control unit 110 may control the rate of change of the EM pressure (P3) for a predetermined duration after detecting the tip-in condition, since the interaction between the gas control circuits is highest during the tip-in condition. As used herein, a "tip-in" condition may be understood as a condition where a rapid change in torque is required, for example, when the rate of change of driver demanded torque is greater than a threshold rate. The driver demand torque may refer to the torque requested by the driver to achieve a particular speed or acceleration. The driver demand torque may correspond to various engine parameters, such as throttle angle. Additionally, the driver demand torque may be determined based on input received from sensors such as a pedal position sensor, a throttle sensor, or a speed sensor.

As detailed with reference to fig. 2, the control unit 110 may determine the driver demand torque based on inputs received from the sensors. In steady state or very slow changing conditions, a nominal set point or default logic may be followed. The control unit 110 may detect a tip-in triggered by a change in the rate of driver demand torque, and then activate a method to limit the rate of change of EM pressure (P3) for a predetermined period of time after the tip-in. Alternatively, the control method may be effective at all times, but will only function during rapidly changing conditions.

In response to detecting a tip-in event, the control unit 110 may set a tip-in flag that is valid for a predetermined period of time. It should be appreciated that the predetermined period of time may be calibrated based on an engine request, such as actual engine torque relative to driver demand torque. For example, the predetermined period of time may increase as the difference between the actual engine torque and the driver requested torque increases. The predetermined period of time may additionally be based on one or more of engine speed, boost pressure, vehicle speed. For example, the predetermined period of time may be higher at higher engine speeds or vehicle speeds than at lower engine speeds or vehicle speeds. Additionally, the predetermined time period may be divided into a plurality of time steps, for example, each time step may be one second, for managing EM pressure in a controlled manner (P3).

The control unit 110 may determine the initial EM pressure after detecting tip-in. In one example, the initial EM pressure may be a modeled value rather than a measured value. Thus, the system without EM pressure measurement can easily implement the mechanisms described herein. The initial EM pressure may be determined from the turbine mass flow (dm _ turbo), the turbine blade angle, and the exhaust pressure downstream of the turbine (P4) based on a model including the EM pressure. However, in other embodiments, the initial EM pressure may also be measured.

The control unit 110 may also determine the immediate position of the EGR valve 162 to calculate a permissible rate of increase in EM pressure. Because the positioning of the EGR valve 162 is typically controlled by the control unit 110, information related to the positioning of the EGR valve 162 may be used by the control unit 110. In one example, the control unit 110 may have EM pressure rate data, such as a look-up table, which may include a maximum rate of rise of EM pressure (P3) as a function of EGR valve position. The rate of increase of the EM pressure (P3) may generally be calibrated such that the permitted rate of increase of the exhaust pressure (P3) is higher when the EGR valve is closed, and decreases with increasing EGR valve opening. Thus, when the EGR valve 162 is open, the rate of increase of the EM pressure may be slower, but when the EGR valve 162 is closed in response to an increase in the EM pressure, the permitted value of the rate of rise of the EM pressure will itself increase.

In one example, the calibration of the maximum permitted EM pressure increase rate and HP EGR valve position may be adjusted according to the maximum valve speed possible and the EGR mass flow error tolerated. For example, the speed at which the HP EGR valve may move may be determined (e.g., the valve may move at a speed of 1 degree valve rotation per millisecond). Additionally, an allowable EGR mass flow error may be calculated (e.g., the allowable EGR mass flow error may be an error in the EGR fraction of 3%, which is then converted to an EGR mass flow error (in kilograms per hour)). Using the orifice flow equation and assuming that the HP EGR valve is moving in the closing direction as quickly as possible (if the EM pressure is increasing), the controller may determine that in the next time step, the maximum EM pressure that may be permitted may be provided without exceeding the allowable EGR mass flow error. In other words, the controller may calculate how much pressure change can be compensated by moving the valve as quickly as possible in one time step based on the maximum valve speed and the orifice flow equation. As such, the orifice flow equation is non-linear. For example, for a given pressure differential across the HP EGR conduit, closing the valve 1 degree when the valve is wide open has a lesser effect on EGR flow, while closing the valve 1 degree when the valve is approaching a closed position has a greater effect on EGR flow. Thus, the allowable pressure change varies non-linearly over a range of valve positions. Based on the initial value of the EM pressure (P3) and the rate of increase of the EM pressure, at each time step, a maximum allowable EM pressure may be calculated. The maximum allowable pressure indicates an EM pressure (P3) to maintain the mass flow of recirculated exhaust gas within permissible limits. For example, the maximum allowable EM pressure may be calculated for a later time step. Thus, the maximum allowable EM pressure increases at each time step according to the maximum permitted rate.

Additionally, at each time step, the position of the blade(s) of the turbine 150 may be determined using the value of the maximum allowable EM pressure at that time step. As previously mentioned, EM pressure is a function of mass flow, downstream turbine pressure, and blade position. Here, this model may be an inverse turbine model, and the maximum allowable EM pressure value, mass flow, and downstream turbine pressure calculated above may be used to determine blade position. Thus, in the present case, the blade position, which determines the EM pressure, is driven by the maximum allowable pressure and cannot be reversed.

Additionally, the control unit 110 may also determine blade positions based on default logic, i.e., logic that may be independent of the maximum allowable EM pressure. Additionally, the default values for blade position may be compared to the blade position determined based on the maximum allowable EM pressure. Based on the comparison, the minimum of the two values of blade position may be selected as the final value of blade position, and the blade may be positioned accordingly. Thus, the resulting EM pressure (P3) may be within the tolerance of the satisfactory EGR control, thereby automatically optimizing both circuits.

Thus, when the EGR valve 160 is fully open, the load rejection capability is poor, while when the EGR valve is closed, there may be no interaction between the two gas control circuits, and the EM pressure (P3) may change without any effect on the EGR circuit.

In this way, the components of fig. 1 realize an engine system comprising: an engine; a turbocharger including an intake air compressor driven by an exhaust gas turbine; a high pressure exhaust gas recirculation (HP EGR) system including an HP EGR conduit and an HP EGR valve for recirculating exhaust gas from upstream of the exhaust turbine to downstream of the intake compressor; a manifold air flow sensor coupled to an engine air intake; and an engine controller comprising computer readable instructions stored on non-transitory memory for: determining an Exhaust Manifold (EM) pressure upstream of the turbine; estimating a maximum allowable rate of increase of the EM pressure based on the position of the HP EGR valve; and adjusting operation of the turbine, including adjusting turbine geometry to maintain the rate of increase of the EM pressure at or below a maximum permitted rate of increase of the EM pressure. The controller may include further instructions for: estimating a maximum EM pressure based on the initial EM pressure and a maximum permitted rate of increase in EM pressure, and wherein adjusting operation of the turbine maintains the estimated EM pressure upstream of the turbine at or below the maximum EM pressure. In another example, the controller may include further instructions for: estimating a mass flow rate of exhaust gas flowing through the turbine; and additionally adjusting operation of the turbine, including adjusting turbine geometry, based on the mass flow rate of exhaust gas through the turbine. In one example, the turbine may be a variable geometry turbine having turbine blades, wherein adjusting the turbine geometry comprises adjusting the turbine blade position, and wherein the initial EM pressure is measured via a sensor or modeled by a controller as a function of each of an exhaust pressure downstream of the turbine, a mass flow rate of exhaust gas flowing through the turbine, and the initial turbine blade position. The controller may include further instructions for: each of the determining, estimating, and adjusting is performed iteratively within each of a plurality of time steps defining a predetermined duration from an increase in the operator requested torque demand. In one example, estimating the maximum EM pressure based on the maximum permitted rate of increase in EM pressure and the initial EM pressure may include: multiplying the maximum permitted rate of increase in EM pressure by the length of the given time step to calculate a maximum permitted increase in EM pressure for the given time step; and adding the maximum permitted increase in EM pressure to the initial EM pressure. The system may further include an exhaust wastegate comprising a wastegate valve coupled across the exhaust turbine, and adjusting operation of the turbine may include adjusting an opening of the wastegate valve to maintain the rate of increase of the EM pressure at or below the maximum permitted rate of increase of the EM pressure. The controller may include further instructions for: the position of the HP EGR valve is changed based on the adjustment operation of the turbine to maintain a substantially constant exhaust flow rate through the HP EGR conduit from before the adjustment operation of the turbine.

Turning now to FIG. 2, a method to control high pressure Exhaust Gas Recirculation (EGR) in a boosted internal combustion engine is shown. The order in which the method 200 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any suitable order to perform the method 200 or an alternative method. In addition, individual blocks may be deleted from method 200 without departing from the spirit and scope of the subject matter described herein. The instructions for implementing the method 200 may be executed by the controller based on instructions stored on a memory of the controller in conjunction with signals received from sensors of the engine system (such as the sensors described above with reference to fig. 1). The controller may employ engine actuators of the engine system to adjust engine operation according to the methods described below. For example, adjusting EGR may include adjusting an actuator coupled to an HP EGR valve based on a measured or modeled exhaust manifold pressure to improve boost response. In one example, the method 200 may be performed by a programmed computing device, such as the control unit 110.

At 202, method 200 includes estimating and/or measuring engine operating conditions. For example, details relating to torque parameters may be obtained. The torque parameters may include, for example, pedal position, engine speed, throttle position, barometric pressure, engine load, boost pressure, and the like. For example, an engine controller (such as control unit 110 of FIG. 1) may receive inputs from various sensors relating to torque parameters. At 204, the method includes determining a rate of change of the driver demand torque using the obtained torque parameter.

At 206, the method includes determining whether the rate of increase of the driver demand torque is greater than a threshold rate. For example, the controller may compare the determined rate of change of driver demand torque to a predetermined and configurable threshold rate. If the rate of change of the driver demand torque is less than the threshold rate, the method 200 may branch to (the "no" branch) block 208. At 208, the method includes controlling operation of the turbocharger based on default logic, and thereby controlling Exhaust Manifold (EM) pressure (P3 of fig. 1). The default logic may include logic that may be independent of the maximum allowable EM pressure, wherein the blade position is not based on the maximum allowable EM pressure. In one example, controlling the turbocharger based on the default logic includes controlling the EM (P3 of fig. 1) pressure based on the default logic.

As one example, the controller may determine a control signal to send to the turbine vane position actuator and/or the wastegate valve, such as a signal indicative of a desired vane or wastegate valve position, the signal determined based on a determination of driver demand torque independent of EGR flow. The controller may determine the control signal to send to the vane position actuator or the wastegate valve by determining to directly account for the driver demanded torque, for example, by increasing the degree of closure of the vane or wastegate valve as the driver demanded torque increases. The controller may determine the position signal based on a calculation using a look-up table, where the input is the driver torque request and the output is the desired position. The routine is then ended.

If it is determined at 206 that the rate of increase of the driver demand torque exceeds the threshold rate, method 200 may proceed to ("yes" branch) 210. At 210, the tip-in flag may be set for a predetermined period of time. In one example, this includes setting a timer. The predetermined period of time may correspond to a period in which the HP EGR valve is expected to respond. In addition, the predetermined time period may be divided into a plurality of time steps or intervals, such as into one second intervals.

At 212, a maximum permissible rate of increase of EM pressure may be determined based on the position of the HP EGR valve. The maximum permissible rate of increase in EM pressure corresponds to the rate of pressure increase that ensures that EM pressure is maintained within allowable limits. A maximum allowable rate of increase in pressure may be determined such that an HP EGR system (such as HP EGR system 160 of fig. 1) may be controlled to appropriately compensate for changes in the pressure differential across an HP EGR conduit (such as HP EGR conduit 12), for example, by changing the position of the HP EGR valve to maintain the flow rate of recirculated exhaust gas within the HP EGR conduit at a desired level. In one example, the controller may receive an immediate value of the EGR valve position and may determine a maximum permissible rate of increase of EM pressure accordingly. Additionally or alternatively, the method may include determining a maximum allowable value for exhaust pressure upstream of the turbine. Operation of the turbocharger assembly may then be controlled such that exhaust pressure upstream of the turbine is maintained at or below a maximum allowable value.

In one example, the controller may reference a map, such as the example map of fig. 3, to determine a maximum permissible rate of increase in EM pressure for a given EGR valve position. Briefly transitioning to FIG. 3, a map 300 illustrates an example relationship 302 between a maximum permissible rate of increase in EM pressure and EGR valve position. Herein, EGR valve position refers to the position of an HP EGR valve coupled in an HP EGR conduit, and the maximum permissible rate of increase of EM pressure refers to the maximum permissible rate of increase of exhaust pressure upstream of an exhaust turbine in a high-pressure exhaust passage. As depicted herein, the relationship 302 between the maximum permissible rate of increase in EM pressure and the HP EGR valve position is non-linear. Specifically, at smaller valve openings, such as at point 304 on map 300, there is choked flow through the HP EGR valve and the flow is extremely insensitive to pressure across the valve. In contrast, at larger valve openings, such as at point 306 on map 300, the flow is sensitive to pressure across the valve, however, HP EGR valve movement has little effect on the flow. For example, for a given pressure differential across the HP EGR conduit, closing the valve 1 degree when the valve is wide open may have a lesser effect on EGR flow, while closing the valve 1 degree when the valve is approaching a closed position may have a greater effect on EGR flow. Thus, the allowable pressure change during a transient may also vary non-linearly over a range of valve positions.

Returning to FIG. 2, the calibration of the maximum allowable rate of increase in EM pressure relative to the HP EGR valve position may be adjusted according to the maximum valve speed possible and the EGR mass flow error tolerated. For example, the speed at which the HP EGR valve may move may be determined (e.g., the valve may move at a speed of 1 degree valve rotation per millisecond). Additionally, an allowable EGR mass flow error may be calculated (e.g., the allowable EGR mass flow error may be an error in the EGR fraction of 3%, which is then converted to an EGR mass flow error (in kilograms per hour)). Using the orifice flow equation and assuming that the HP EGR valve is moving in the closing direction as quickly as possible (if the EM pressure is increasing), the controller may determine that the maximum EM pressure that may be permitted may be provided without exceeding the allowable EGR mass flow error. In other words, the controller may calculate how much pressure change can be compensated by moving the valve as quickly as possible in one time step based on the maximum valve speed and the orifice flow equation.

The effect of a change in exhaust pressure within an HP exhaust conduit (e.g., HP exhaust conduit 9b of fig. 1) relative to inlet gas pressure within an HP intake conduit (e.g., HP intake conduit 6b of fig. 1) on the flow rate of EGR gas within an HP EGR conduit (such as HP EGR conduit 12 of fig. 1) may depend on the position of an HP EGR valve (e.g., HP EGR valve 162 of fig. 1). Maximum admission of pressureThe rate of increase and/or the maximum allowable pressure value may be determined based at least in part on a position of the HP EGR valve. The maximum permitted rate of increase may be determined by reference to a data model or a look-up table. For example, the maximum allowable rate of pressure increase may be determined by reference to a data model that provides the maximum allowable rate of pressure increase according to equation (1) as a function of the position of the HP EGR valve, where Δ P_3maxIs the maximum permitted rate of increase in exhaust pressure upstream of the turbine.

ΔP_3max＝F₁(EGR valve position) (1)

At 214, the method includes determining an initial or current value of EM pressure. In one example, the initial EM pressure is based on an output of an exhaust pressure sensor. Alternatively, the initial EM pressure may be modeled using a turbine model based on the exhaust pressure downstream of the turbine (e.g., P4 of fig. 1), the turbine mass flow, and the vane position of the turbine. For example, the initial values may be measured in real time based on the exhaust pressure value downstream of the turbine (P4), the turbine mass flow, and the blade position of the turbine.

At 216, the method includes determining a maximum permissible value of EM pressure. The maximum allowable EM pressure may be calculated based on the maximum rate of increase of the EM pressure and an initial value of the EM pressure. In one example, the calculation is performed iteratively at each interval or time step of the predetermined period. Thus, at each time step, the value of the maximum allowable EM pressure may increase.

At 218, using the maximum allowable EM pressure, the blade position may be determined. For example, the vane position may be determined using a reverse turbine model, where the vane position is set according to the maximum allowable EM pressure, the exhaust gas pressure downstream of the turbine, and the mass flow rate of the exhaust gas in the turbine.

Alternatively, the minimum of the blade position determined based on the maximum allowable EM pressure and the blade position determined based on the default logic is calculated to determine the final blade position. Thus, the vane position may always be the lowest (maximum open) possible vane position. The low set point of the turbine may be a more open position giving a lower EM pressure. In this way, the calculated maximum EM pressure only works when the set point from the default logic will cause a higher EM pressure (with a more closed blade position). If the driver does not request a large torque increase (or a rapid increase in torque), then the blade position limitation is not effective.

At 220, the blade(s) of the turbine may be actuated to the determined position to maintain the EM pressure within allowable limits. For example, the controller may send a signal to the VGT to position the blades of the turbine based on the determined blade position. Accordingly, the mass flow of EGR may be maintained within a permissible limit to ensure that the EM pressure does not exceed the previously determined maximum allowable EM pressure, as the permissible limit for the mass flow of EGR is based on the maximum allowable EM pressure.

At 222, it is determined whether a predetermined period of time has elapsed, such as based on an output of a timer. If not, the method returns to 214 to iteratively update the estimate of the initial pressure, and then the maximum allowable EM pressure, and then the position of the blade. In one example, the maximum EM pressure determined on a given iteration may be used as the initial EM pressure on the immediately subsequent iteration. Specifically, the previously determined maximum allowable pressure becomes the initial EM pressure for the current time step. Alternatively, a new value for the initial EM pressure may be determined on each iteration. The new values may correspond to modeled values, or may be measured in real time, as discussed at 214. If the predetermined period of time has elapsed, the routine clears the tip-in flag at 224 and returns to controlling the VGT vane position based on default logic at 208. Accordingly, the blade position after the expiration of the predetermined time period may be controlled based on default logic.

In one example, determining the vane position based on the maximum allowable EM pressure may include determining a desired geometry setting of the VGT (e.g., an angle of a variable vane of the VGT) and/or a desired position of the wastegate valve, and setting the geometry of the VGT and/or the position of the wastegate valve according to the determined settings. The desired setting may be determined by reference to a data model and a look-up table. In one example, a data model is applied that allows for a maximum allowable pressure value to be relied uponThe mass flow rate of exhaust gas through the turbine, and the pressure downstream of the turbine, for example, are determined according to equation (2) to determine a VGT geometry setting, where P_3maxIs the maximum permitted value or pressure and,

is the mass flow rate of exhaust gas through the turbine, and P₄Is the exhaust pressure downstream of the turbine.

In this way, the maximum allowable pressure value may be calculated by: the maximum permitted rate of increase in pressure is multiplied by the time step at which each iteration of the method is performed and the result is added to the initial exhaust pressure estimate.

As described above, an increase in exhaust gas pressure upstream of the turbine may be caused by a change in the flow area of the exhaust gas flowing through and/or around the turbine. The increase in pressure caused by a particular change in flow area may depend on the mass flow rate of exhaust gas flowing through and/or bypassing the turbine. Accordingly, the method may further include determining a mass flow rate of exhaust gas through and/or around the turbine. Operation of the turbine may be controlled at least partially in accordance with the determined mass flow rate, for example, to maintain a rate of increase of exhaust pressure upstream of the turbine at or below a maximum permitted rate.

The mass flow rate of exhaust gas flowing through the turbine may depend on the exhaust pressure downstream of the turbine. As shown in FIG. 1, the engine assembly may also include a Low Pressure (LP) EGR system, and the position of the LP EGR valve may therefore affect the mass flow rate of exhaust gas through the turbine. Specifically, LP EGR provides efficiency benefits because EGR that has passed through the LP EGR path has released more exhaust energy to the turbine (as compared to EGR via the HP EGR path). Thus, in addition to adjusting the position of the vanes, the position of the LP EGR valve may be adjusted to limit EM pressure in response to an increase in driver demand torque.

In one example, the split ratio of total EGR between the low pressure route and the high pressure route may be changed to achieve the exhaust NOx target. Additionally, as the EM pressure increases as the vanes move to a more closed position, LP EGR flow may be reduced (by decreasing the opening of the LP EGR valve) to compensate for the increased HP EGR flow. However, since the exhaust flow path of LP EGR to the engine is much longer than HP EGR, their response times are different. Additionally, the pressure gradient across the LP EGR system is much lower than the pressure gradient across the HP EGR system. Thus, to compensate for rapidly changing VGT vane position and HP EGR flow using slowly changing farther LP EGR flow, LP-EGR may be treated as a slowly changing "noise factor" for VGT and HP-EGR control, which is more "busy" during transients. Additionally, because operation of the exhaust aftertreatment device may affect the mass flow rate of exhaust gas through the exhaust system, and thus through the turbine, in addition to adjusting the position of the vanes, exhaust aftertreatment device operation is adjusted to limit EM pressure in response to an increase in driver demand torque. For example, after a period of operation of the exhaust aftertreatment device, the performance of the device may decrease. For example, the particulate filter and/or the lean NOx trap may become full, thereby reducing the rate at which the particulate filter and/or the lean NOx trap can remove pollutants from the exhaust. When the performance of the exhaust aftertreatment device decreases, the mass flow rate of the exhaust gas through the exhaust aftertreatment device and/or the pressure differential across the exhaust aftertreatment device may change. Operation of the exhaust aftertreatment device may therefore affect the mass flow rate of exhaust gas through the turbine, as well as the exhaust gas pressure downstream (immediately downstream) of the turbine. These factors may in turn affect the estimated EM pressure upstream of the turbine. For example, an exhaust aftertreatment device regeneration or purging event may be suspended in response to a transient increase in torque demand due to tip-in. This is because the effects of aftertreatment devices (e.g., filter plugging) are slowly changing, and the actions taken in response (e.g., filter regeneration or NOx-trap cleaning) take several minutes to complete.

In this way, by determining the exhaust gas pressure upstream of the turbine and/or the mass flow rate of exhaust gas through the turbine, the turbocharger assembly may be more accurately controlled to reduce the undesirable increase in the flow rate of exhaust gas through the HP EGR conduit. Thus, an undesirable reduction in the power provided by the engine is reduced.

It should be appreciated that the iterative process of the method of fig. 2 may optionally be performed continuously during operation of the vehicle, e.g., in a continuous loop. In other words, the iterative process may be performed regardless of whether the driver of the vehicle, the engine controller, or another controller of the vehicle has requested an increase in torque to be provided. For example, the method may be triggered when any request for an increased amount of torque supplied by the engine is detected.

Turning now to FIG. 4, exemplary engine operation is illustrated with coordination of HP EGR circuit and boost circuit control. Map 400 depicts the operator torque demand via Pedal Position (PP) at curve 402, the position of the HP EGR valve coupled in the HP EGR conduit at curve 404, the maximum permitted Exhaust Manifold (EM) pressure upstream of the exhaust turbine at curve 406, the turbine vane position at curve 408, and the boost pressure at the turbocharger compressor at curve 410. The maximum allowable EM pressure upstream of the exhaust turbine is determined from the maximum allowable rate of increase of EM pressure, which in turn is determined from the HP EGR valve position.

Prior to t1, the engine is operated at a certain boost pressure (curve 410) in accordance with a lower operator torque request (curve 402). A lower level of boost pressure is provided by maintaining the turbine vanes of the turbocharger more open (curve 408). The engine also operates with a reduced amount of HP EGR, as indicated by the smaller opening of the HP EGR valve (curve 404).

At t1, there is a rapid increase in operator torque demand due to the tip-in event. A maximum allowable EM pressure is determined in response to the increased operator torque request. Specifically, a higher rate of increase in EM pressure is permitted due to the more closed position of the HP EGR valve when the accelerator pedal is depressed, allowing for a higher maximum permitted EM pressure. Specifically, due to the more closed position of the HP EGR valve, the boost circuit is less likely to be adversely affected by the HP EGR circuit, and thus the EM pressure is allowed to increase to a higher level. The increase in EM pressure is achieved by moving the vanes to a more closed position, allowing the boost pressure to increase rapidly. At t2, once the torque demand is reduced, the vane position returns to a more open position with a corresponding drop in boost pressure.

At t3, there is a change in engine operating conditions that causes an increase in the demand for HP EGR. This is satisfied by moving the HP EGR valve to a more open position. At t4, there is another rapid increase in operator torque demand due to another tip-in event. A maximum allowable EM pressure is determined in response to the increased operator torque request. Specifically, due to the more open position of the HP EGR valve when the accelerator pedal is depressed, a relatively lower rate of increase in EM pressure is permitted (as compared to the rate permitted at t 1), allowing for a lower maximum permitted EM pressure (as compared to the EM pressure permitted at t 1). Specifically, due to the more open position of the HP EGR valve, the boost circuit is more likely to be adversely affected by the HP EGR circuit, and thus allows the EM pressure to increase to a lower level. A small increase in EM pressure is achieved by: move the vanes to a less closed position and keep the vanes less closed for the duration from t4 to t 5. This duration corresponds to the duration that the HP EGR valve is gradually moved to a more closed position to reduce the effect that the HP EGR loop may have on the boost circuit. Specifically, between t4 and t5, the position of the HP EGR valve is adjusted based on the adjustment of the vane position, and the maximum allowable EM pressure is increased in order to maintain a substantially constant exhaust flow rate through the HP EGR conduit from before the adjustment operation of the turbine. That is, HP EGR flow may be maintained from before t4, through t5, and thereafter by adjusting the HP EGR valve in coordination with the adjustment of vane position. This is because as the vane position moves to a more closed position and the EM pressure increases, the pressure differential across the EGR duct increases. This increase in pressure differential, if the position of the HP EGR valve is maintained, will cause a rise in HP EGR flow into the intake manifold, degrading engine performance. Conversely, by adjusting the HP EGR valve position in coordination with the vane position adjustment, EGR flow is maintained even as pressure upstream of the inlet of the HP EGR conduit increases.

As a result of the vane and EGR valve position adjustments, between t4 and t5, the boost pressure begins to gradually increase. At t5, once the HP EGR valve has moved to a more closed position, wherein the EGR circuit has a reduced effect on the boost circuit, the vanes move to a more closed position. Therefore, after t5, the boost pressure begins to increase more quickly to the boost level that meets the operator torque request. It should be appreciated that if the vanes are moved directly to a more closed position at t4 (as indicated by dashed line segment 409) in response to an increasing operator torque request while the HP EGR valve remains in its more open position, EGR is received in the intake passage, thereby reducing engine torque output and reducing compressor boost pressure (as indicated by dashed line segment 411).

At t6, once the torque demand is reduced, the vane position returns to a more open position with a corresponding drop in boost pressure. At t7, there is a change in engine operating conditions that causes an increase in the demand for HP EGR. This is satisfied by moving the HP EGR valve to a more open position.

In this way, the vane position of the turbine can be changed in a controlled manner during rapidly changing conditions, minimizing interference with both the exhaust control loop and the boost control loop, and also optimizing the performance of both loops. A technical effect of controlling the position of the turbine blades based on the maximum allowable EM pressure is to allow only a limited portion of the exhaust gas to enter the intake manifold. Accordingly, the EM pressure may be maintained within permissible limits to avoid any adverse impact on the boost circuit and thus on the performance of the engine. By simultaneously adjusting the HP EGR valve position as the vane position and exhaust pressure upstream of the turbine vary, EGR flow may be maintained as boost pressure increases, thereby improving boost engine performance.

Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The control methods and programs disclosed herein may be stored as executable instructions in a non-transitory memory and may be implemented by a control system including a controller in conjunction with various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various acts, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and/or functions may be repeatedly performed depending on the particular strategy being used. Additionally, the described acts, operations, and/or functions may graphically represent code to be programmed into the non-transitory memory of the computer readable storage medium in the engine control system, wherein the described acts are implemented by execution of the instructions in conjunction with the electronic controller in a system that includes various engine hardware components.

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above techniques may be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the inventions includes all novel and non-obvious combinations and subcombinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.

Claims

1. A method for a turbocharged engine, comprising:

estimating a maximum allowable rate of increase of exhaust manifold pressure, or EM pressure, based on a position of a high pressure exhaust gas recirculation valve, or HP EGR valve;

estimating a maximum allowable EM pressure based on the maximum allowable rate of increase of EM pressure; and

adjusting a blade position of an exhaust turbine based on the maximum allowable EM pressure,

wherein the HP EGR valve is coupled in a high pressure EGR passage that recirculates exhaust gas from upstream of the exhaust turbine to downstream of an intake compressor.

2. The method of claim 1, further comprising estimating an initial value of the EM pressure based on each of an exhaust pressure downstream of the exhaust turbine, a turbine mass flow, and an initial vane position, and wherein the maximum allowable EM pressure is further based on the initial value of the EM pressure.

3. The method of claim 1, wherein said maximum allowable rate of increase of said estimated EM pressure, said estimated maximum allowable EM pressure, and said adjusting said blade position are performed over a predetermined period of time in response to a rate of change of estimated driver demand torque being greater than a threshold rate.

4. The method of claim 3, further comprising, when the rate of change of the estimated driver demand torque is greater than the threshold rate, adjusting the position of the HP EGR valve based on the maximum allowable EM pressure and the vane position to maintain an EGR flow rate while adjusting the vane position.

5. The method of claim 1, wherein the adjusting the vane position comprises determining, via a reverse turbine model, a final vane position as a function of the maximum allowable EM pressure, an exhaust pressure downstream of the turbine, and a mass flow rate of the exhaust gas through the turbine.

6. The method of claim 5, wherein adjusting the vane position further comprises:

calculating a default blade position independent of the maximum allowable EM pressure;

selecting a minimum value for the final blade position based on the maximum allowable EM pressure and the default blade position; and

positioning the blade according to the selection.

7. The method of claim 1, wherein said adjusting said vane position maintains said EM pressure estimated upstream of said exhaust turbine and at an inlet of said high pressure EGR passage at or below said maximum allowable EM pressure.

8. The method of claim 7, further comprising adjusting a position of a low pressure EGR valve coupled in a low pressure EGR passage that recirculates exhaust gas from downstream of the exhaust turbine to upstream of an intake compressor based on the adjusted vane position.

9. An engine system, comprising:

an engine;

a turbocharger including an intake air compressor driven by an exhaust gas turbine;

a high pressure exhaust gas recirculation (HP EGR) system including an HP EGR conduit and an HP EGR valve for recirculating exhaust gas from upstream of the exhaust turbine to downstream of the intake compressor;

a manifold air flow sensor coupled to an engine air intake; and

an engine controller comprising computer readable instructions stored on a non-transitory memory for:

determining an exhaust manifold pressure (EM pressure) upstream of the turbine;

estimating a maximum allowable rate of increase of EM pressure based on the position of the HP EGR valve; and

adjusting operation of the turbine, including adjusting turbine geometry, to maintain a rate of increase of EM pressure at or below the maximum permitted rate of increase of EM pressure.

10. The system of claim 9, wherein the controller comprises further instructions for:

estimating a maximum EM pressure based on the maximum permitted rate of increase of EM pressure and an initial EM pressure, and wherein the adjusting operation of the turbine maintains the EM pressure estimated upstream of the turbine at or below the maximum EM pressure.

11. The system of claim 10, wherein the controller comprises further instructions for:

estimating a mass flow rate of exhaust gas flowing through the turbine; and

further adjusting operation of the turbine, including adjusting the turbine geometry, based on the mass flow rate of exhaust gas through the turbine.

12. The system of claim 11, wherein the turbine is a variable geometry turbine having turbine blades, wherein adjusting turbine geometry comprises adjusting turbine blade position, and wherein the initial EM pressure is measured via a sensor or modeled by the controller from each of an exhaust pressure downstream of the turbine, the mass flow rate of exhaust gas flowing through turbine, and initial turbine blade position.

13. The system of claim 10, wherein the controller includes further instructions for iteratively performing each of the determining, estimating, and adjusting within each of a plurality of time steps defining a predetermined duration from an increase in operator requested torque demand.

14. The system of claim 13, wherein estimating the maximum EM pressure based on the maximum permitted rate of increase in EM pressure and the initial EM pressure comprises:

multiplying the maximum permitted rate of increase in EM pressure by a length of a given time step to calculate a maximum permitted increase in EM pressure for the given time step; and

adding the maximum permitted increase in EM pressure to the initial EM pressure.

15. The system of claim 9, further comprising an exhaust wastegate comprising a wastegate valve coupled across the exhaust turbine, and wherein adjusting operation of the turbine comprises adjusting an opening of the wastegate valve to maintain a rate of increase of EM pressure at or below the maximum permitted rate of increase of EM pressure.

16. The system of claim 9, wherein the controller comprises further instructions for:

changing a position of the HP EGR valve based on the adjustment operation of the turbine to maintain a substantially constant exhaust flow rate through the HP EGR conduit from before the adjustment operation of the turbine.

17. A method for a turbocharged engine, comprising:

in response to an increase in the operator torque request,

estimating a maximum allowable rate of increase of exhaust pressure upstream of the variable geometry exhaust turbine based on the high-pressure EGR valve position; and

adjusting a vane position of the turbine based on the maximum permitted rate of increase to maintain the exhaust pressure upstream of the turbine at or below a threshold pressure.

18. The method of claim 17, further comprising, when adjusting the vane position, adjusting the high-pressure EGR valve position based on the adjusted vane position to maintain an EGR flow rate through the high-pressure valve.

19. The method of claim 17, further comprising, via a reverse turbine model, modeling an initial exhaust pressure upstream of the exhaust turbine as an operator torque request increases according to each of: a turbine mass flow, an exhaust pressure downstream of the exhaust turbine, and an initial vane position as the operator torque request increases, and wherein the threshold pressure is based on each of the maximum permitted rate of increase of upstream exhaust pressure and the modeled initial exhaust pressure.

20. The method of claim 17, further comprising adjusting an opening of an exhaust wastegate valve coupled across the turbine based on the maximum permitted rate of increase and the adjusted vane position to maintain the exhaust pressure upstream of the turbine at or below the threshold pressure.